1. Field of the Invention
The present invention relates to a drive system, a video device, an image projection device, and a drive control method.
2. Description of the Related Art
A piezoelectric element is known to exert a so-called inverse piezoelectric effect that when applied with voltage in a direction of electrodes, deforms, i.e., contracts in proportion to an electrical potential of the applied voltage. Conventionally, there is developed a piezoelectric actuator that transmits a driving force to a driven body by using such a piezoelectric element.
A piezoelectric element used in a piezoelectric actuator exerts a driving force in a state of being polarized in one direction, for example, like a permanent magnet; its driving force can be obtained by connecting the output of a drive circuit to between electrodes installed on both end faces of the piezoelectric element in a polarization direction. The above-mentioned polarization is obtained by continuing to apply a constant voltage for a predetermined period of time in consideration of the composition of the element. The element which has had polarization is driven by being applied with voltage in between a direction of the voltage that has caused the polarization and zero in general.
Conventionally, to maintain polarization of a piezoelectric element, the piezoelectric element is driven by positive voltage from the ground (GND). An actuator composed of a piezoelectric element basically has the structure of a capacitor. Therefore, its capacity is very large, and it is difficult to drive the actuator with a general operational amplifier. Accordingly, in general, a circuit that amplifies current is added to the output stage of the amplifier. However, there is a problem that the output from GND is impossible with a single supply (a positive supply only), so a negative supply is required structurally, which results in a substantial increase in cost.